阅读说明：本技术 一种β-碳化硅微粉的提纯方法 (Purification method of beta-silicon carbide micro powder ) 是由 韩凤兰 祁利民 张巧琴 张深根 吴澜尔 朱颖 袁银凤 黄玉才 卢江龙 尹旭帆 马 于 2021-03-17 设计创作，主要内容包括：本发明提供了一种β-碳化硅微粉的提纯方法,属于陶瓷材料技术领域。本发明以硫酸溶液和氢氟酸为腐蚀剂,分两步对碳化硅微粉进行化学提纯,首先利用硫酸与铁的氧化反应去除铁单质,再利用氟离子与硅的氟化反应去除游离硅,并通过控制氧化反应和氟化反应的温度和时间以及原料的比例,在保证碳化硅微粉纯度的同时,实现高效提纯。实验结果表明,本发明提供的提纯方法中化学反应在1h左右,碳化硅微粉的纯度在99.42％以上。(The invention provides a purification method of beta-silicon carbide micropowder, belonging to the technical field of ceramic materials. The method takes sulfuric acid solution and hydrofluoric acid as corrosive agents, and carries out chemical purification on the silicon carbide micro powder in two steps, wherein the iron simple substance is removed by using the oxidation reaction of sulfuric acid and iron, the free silicon is removed by using the fluorination reaction of fluorine ions and silicon, and the high-efficiency purification is realized while the purity of the silicon carbide micro powder is ensured by controlling the temperature, the time and the raw material ratio of the oxidation reaction and the fluorination reaction. Experimental results show that the chemical reaction in the purification method provided by the invention is about 1h, and the purity of the silicon carbide micro powder is more than 99.42%.)

1. A method for purifying beta-silicon carbide micropowder comprises the following steps:

(1) mixing the silicon carbide dry powder with a sulfuric acid solution and water, and carrying out oxidation reaction to obtain a silicon carbide suspension; the mass concentration of the sulfuric acid solution is 50-60%; the temperature of the oxidation reaction is 70-90 ℃, and the time is 25-40 min;

(2) mixing the silicon carbide suspension obtained in the step (1) with hydrofluoric acid, and carrying out fluorination reaction to obtain beta-silicon carbide micro powder; the mass concentration of the hydrofluoric acid is 20-30%; the temperature of the fluorination reaction is 70-90 ℃, and the time is 25-40 min;

the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: (0.15-0.4) mL;

the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (5-15) g: 1 mL.

2. The purification method according to claim 1, wherein the mass content of impurities in the silicon carbide dry powder in the step (1) is 10-30%.

3. The purification method according to claim 1, wherein the sulfuric acid solution in the step (1) has a mass concentration of 55 to 58%.

4. A purification method according to claim 2 or 3, wherein the ratio of the mass of the dry silicon carbide powder to the volume of the sulfuric acid solution is 1 g: (0.2-0.35) mL.

5. The purification method according to claim 1, wherein the ratio of the mass of the silicon carbide dry powder to the volume of water in step (1) is 1 g: (1-2) mL.

6. The purification method according to claim 1, wherein the temperature of the oxidation reaction in the step (1) is 80 to 85 ℃ and the time of the oxidation reaction is 30 to 35 min.

7. The purification method according to claim 1, wherein the pH of the silicon carbide suspension in the step (1) is 4 to 5.

8. The purification method according to claim 1, wherein the concentration by mass of the hydrofluoric acid in the step (2) is 25 to 28%.

9. The purification method according to claim 8, wherein the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (10-13) g: 1 mL.

10. The purification method according to claim 1, wherein the temperature of the fluorination reaction in the step (2) is 80 to 85 ℃ and the time of the fluorination reaction is 30 to 35 min.

Technical Field

The invention belongs to the technical field of ceramic materials, and particularly relates to a method for purifying beta-silicon carbide micro powder.

Background

Silicon carbide (SiC) micropowder is widely applied to the technical fields of aerospace, petroleum and petrochemical industry, precision machining, equipment sealing and the like because of the characteristics of high hardness, high grinding capacity, high temperature resistance, thermal shock resistance, corrosion resistance and good dielectric property. Due to the particularity of the synthesis method, impurities such as free silicon, iron simple substance and the like can be remained in the silicon carbide, and the quality and the performance of the silicon carbide ceramic material produced by taking the micro powder as the material are seriously influenced. Therefore, it is necessary to purify the fine silicon carbide powder.

At present, the purification of silicon carbide micropowder is mainly carried out by using an acidic solution, for example, patent CN102311115A describes a method for chemically purifying silicon carbide micropowder according to the following steps: water: sulfuric acid: 200 parts of hydrofluoric acid: (180-220): (7-10): (0.5-2), adding the materials into a slurry preparation tank in sequence according to the proportion, fully stirring, reacting for 8-10 h, deacidifying by using a centrifugal machine, and transferring the centrifugal mortar to a rinsing tank for acid bleaching. Although the method can obtain the silicon carbide micro powder with the purity of more than 99 percent, the purification process only needs 8-10 hours of chemical reaction, takes longer time and is not beneficial to industrial production.

Therefore, it is necessary to improve the method for purifying the fine silicon carbide powder so as to achieve the purpose of purifying the fine silicon carbide powder with high efficiency and to obtain the fine silicon carbide powder with high purity.

Disclosure of Invention

The invention aims to provide a method for purifying beta-silicon carbide micro powder. The purification method provided by the invention can be used for efficiently purifying the silicon carbide micro powder, and the obtained silicon carbide micro powder has higher purity.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a purification method of beta-silicon carbide micro powder, which comprises the following steps:

(1) mixing the silicon carbide dry powder with a sulfuric acid solution and water, and carrying out oxidation reaction to obtain a silicon carbide suspension; the mass concentration of the sulfuric acid solution is 50-60%; the temperature of the oxidation reaction is 70-90 ℃, and the time is 25-40 min;

(2) mixing the silicon carbide suspension obtained in the step (1) with hydrofluoric acid, and carrying out fluorination reaction to obtain beta-silicon carbide micro powder; the mass concentration of the hydrofluoric acid is 20-30%; the temperature of the fluorination reaction is 70-90 ℃, and the time is 25-40 min;

the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: (0.15-0.4) mL;

the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (5-15) g: 1 mL.

Preferably, the mass content of impurities in the silicon carbide dry powder in the step (1) is 10-30%.

Preferably, the mass concentration of the sulfuric acid solution in the step (1) is 55-58%.

Preferably, the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: (0.2-0.35) mL.

Preferably, the ratio of the mass of the silicon carbide dry powder to the volume of the water in the step (1) is 1 g: (1-2) mL.

Preferably, the temperature of the oxidation reaction in the step (1) is 80-85 ℃, and the time of the oxidation reaction is 30-35 min.

Preferably, the pH value of the silicon carbide suspension in the step (1) is 4-5.

Preferably, the mass concentration of the hydrofluoric acid in the step (2) is 25-28%.

Preferably, the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (10-13) g: 1 mL.

Preferably, the temperature of the fluorination reaction in the step (2) is 80-85 ℃, and the time of the fluorination reaction is 30-35 min.

The invention provides a purification method of beta-silicon carbide micro powder, which comprises the following steps: mixing the silicon carbide dry powder with a sulfuric acid solution and water, and carrying out oxidation reaction to obtain a silicon carbide suspension; the mass concentration of the sulfuric acid solution is 50-60%; the temperature of the oxidation reaction is 70-90 ℃, and the time is 25-40 min; mixing the silicon carbide suspension with hydrofluoric acid to perform fluorination reaction to obtain beta-silicon carbide micro powder; the mass concentration of the hydrofluoric acid is 20-30%; the temperature of the fluorination reaction is 70-90 ℃, and the time is 25-40 min; the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: (0.15-0.4) mL; the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (5-15) g: 1 mL. The method takes sulfuric acid solution and hydrofluoric acid as corrosive agents, and carries out chemical purification on the silicon carbide micro powder in two steps, wherein the iron simple substance is removed by using the oxidation reaction of sulfuric acid and iron, the free silicon is removed by using the fluorination reaction of fluorine ions and silicon, and the high-efficiency purification is realized while the purity of the silicon carbide micro powder is ensured by controlling the temperature, the time and the raw material ratio of the oxidation reaction and the fluorination reaction. Experimental results show that the chemical reaction in the purification method provided by the invention is about 1h, and the purity of the silicon carbide micro powder is more than 99.42%.

Drawings

FIG. 1 is a macroscopic view of a suspension obtained after mixing a dry powder of silicon carbide with water in example 1;

FIG. 2 is a macroscopic view of a suspension obtained by completion of the fluorination reaction in example 1;

FIG. 3 is a macroscopic view of the fine β -silicon carbide powder purified in example 1.

Detailed Description

The invention provides a purification method of beta-silicon carbide micro powder, which comprises the following steps:

(1) mixing the silicon carbide dry powder with a sulfuric acid solution and water, and carrying out oxidation reaction to obtain a silicon carbide suspension; the mass concentration of the sulfuric acid solution is 50-60%; the temperature of the oxidation reaction is 70-90 ℃, and the time is 25-40 min;

(2) mixing the silicon carbide suspension obtained in the step (1) with hydrofluoric acid, and carrying out fluorination reaction to obtain beta-silicon carbide micro powder; the mass concentration of the hydrofluoric acid is 20-30%; the temperature of the fluorination reaction is 70-90 ℃, and the time is 25-40 min;

the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: (0.15-0.4) mL;

the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (5-15) g: 1 mL.

The purification method provided by the invention is suitable for preparing the silicon carbide dry powder material by the conventional method in the prior art. In the invention, the mass content of impurities in the silicon carbide dry powder is preferably 10-30%, and more preferably 15-25%; the species of the impurities preferably include elemental iron and free silicon.

The invention mixes the silicon carbide dry powder with sulfuric acid solution and water to carry out oxidation reaction, and obtains silicon carbide suspension. The invention adopts the mixing of sulfuric acid solution and silicon carbide dry powder, and removes the impurity iron simple substance in the silicon carbide dry powder by the oxidation reaction of sulfuric acid and iron.

In the invention, the mass concentration of the sulfuric acid solution is 50-60%, preferably 55-58%. The method for preparing the sulfuric acid solution is not particularly limited in the present invention, and the sulfuric acid solution may be prepared by a method known to those skilled in the art. In the invention, when the mass concentration of the sulfuric acid solution is in the range, the content of hydrogen ions in the sulfuric acid solution can be ensured, so that the iron impurity can be effectively removed.

In the invention, the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: (0.15-0.4) mL, preferably 1 g: (0.2-0.35) mL, more preferably 1 g: 0.3 mL. In the present invention, when the ratio of the mass of the silicon carbide dry powder to the volume of the sulfuric acid solution is within the above range, the time for the oxidation reaction can be shortened, and the efficient purification of the silicon carbide fine powder can be achieved.

In the present invention, the water is preferably tap water or deionized water. The source of the water is not particularly limited in the present invention, and a commercially available product known to those skilled in the art may be used. In the present invention, the water acts as a solvent for dissolving the dry silicon carbide powder.

In the present invention, the ratio of the mass of the dry silicon carbide powder to the volume of water is preferably 1 g: (1-2) mL, more preferably 1 g: 1.5 mL. In the invention, when the mass-to-volume ratio of the silicon carbide dry powder to water is in the above range, the dissolution of the raw material can be ensured without wasting water resources.

In the present invention, the operation of mixing the silicon carbide dry powder with the sulfuric acid solution and water is preferably: the silicon carbide dry powder is mixed with water and then with a sulfuric acid solution. The operation of mixing the silicon carbide dry powder with water and then with the sulfuric acid solution is not particularly limited in the invention, and the technical scheme for preparing the mixed material, which is well known to the technical personnel in the field, is adopted. In the invention, the dry silicon carbide powder is mixed with water and then mixed with the sulfuric acid solution, so that the mixing degree of the raw materials can be improved.

In the invention, the temperature of the oxidation reaction is 70-90 ℃, and preferably 80-85 ℃; the time of the oxidation reaction is 25-40 min, preferably 30-35 min. In the present invention, when the temperature of the oxidation reaction is within the above range, the time of the oxidation reaction can be shortened, and the silicon carbide fine powder can be efficiently purified.

In the present invention, the oxidation reaction is preferably carried out in a constant-temperature water bath. The type of the constant-temperature water bath kettle is not specially limited, and the constant-temperature water bath kettle known by the technical personnel in the field can be adopted.

After the oxidation reaction is completed, the invention preferably sequentially cools and washes the product obtained from the oxidation reaction to obtain a silicon carbide suspension.

The cooling operation is not particularly limited in the present invention, and the product obtained by the oxidation reaction is cooled to room temperature.

In the invention, the water used for washing is preferably tap water or deionized water; the water washing is preferably: and mixing the product obtained by cooling with water, settling, and then discharging the supernatant to obtain the silicon carbide suspension. The operation of mixing with water, settling and discharging the supernatant is not particularly limited, and the pH of the silicon carbide suspension is ensured to be 4-5. In the invention, the pH value of the silicon carbide suspension is 4-5, which is beneficial to the subsequent reaction.

After the silicon carbide suspension is obtained, the silicon carbide suspension is mixed with hydrofluoric acid to carry out fluorination reaction, and the beta-silicon carbide micro powder is obtained. According to the invention, the silicon carbide suspension is mixed with hydrofluoric acid, and the fluorine ion and silicon fluorination reaction is utilized to remove impurity free silicon in the silicon carbide dry powder.

In the present invention, the mass concentration of the hydrofluoric acid is 20 to 30%, and more preferably 25 to 28%. The method for preparing the hydrofluoric acid is not particularly limited in the present invention, and the hydrofluoric acid may be prepared by a method known to those skilled in the art. In the invention, when the mass concentration of the hydrofluoric acid is in the range, the content of fluorine ions can be ensured, so that the impurity free silicon can be effectively removed.

In the invention, the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is (5-15) g: 1mL, more preferably (10 to 13) g: 1 mL. In the invention, when the mass ratio of the silicon carbide dry powder to the hydrofluoric acid is in the range, the fluorination reaction time can be shortened, and the silicon carbide micro powder can be efficiently purified.

In the present invention, the operation of mixing the silicon carbide suspension with hydrofluoric acid is preferably to add hydrofluoric acid to the silicon carbide suspension. The operation of adding hydrofluoric acid to the silicon carbide suspension is not particularly limited, and a mixing operation known to those skilled in the art may be used.

In the invention, the temperature of the fluorination reaction is 70-90 ℃, preferably 80-85 ℃; the time of the fluorination reaction is 25-40 min, preferably 30-35 min. In the present invention, when the temperature and time of the fluorination reaction are within the above ranges, the time of the fluorination reaction can be shortened, and the silicon carbide fine powder can be efficiently purified.

In the present invention, the fluorination reaction is preferably carried out in a constant-temperature water bath. The type of the constant-temperature water bath kettle is not specially limited, and the constant-temperature water bath kettle known by the technical personnel in the field can be adopted.

After the fluorination reaction is finished, the invention preferably sequentially cools, washes and dries the product obtained by the fluorination reaction to obtain the beta-silicon carbide micro powder.

The cooling operation is not particularly limited in the present invention, and the product obtained by the fluorination reaction is cooled to room temperature.

In the present invention, the washing with water is preferably performed by repeating washing with deionized water and filtration, and then washing with purified water and filtration, in the product obtained by cooling.

The invention has no special limit on the times of repeatedly adding water for washing and filtering until the pH value of the supernatant is between 6 and 7. In the present invention, the number of the repeated purified water washing is preferably 3 times.

The drying operation is not particularly limited in the present invention, and may be a drying operation known to those skilled in the art.

According to the method, a sulfuric acid solution and hydrofluoric acid are used as corrosive agents, the silicon carbide micro powder is chemically purified in two steps, iron simple substances are removed by using an oxidation reaction of sulfuric acid and iron, free silicon is removed by using a fluorination reaction of fluorine ions and silicon, the degree of the oxidation reaction and the fluorination reaction can be improved, the purity of the silicon carbide micro powder is improved, and efficient purification is realized while the purity of the silicon carbide micro powder is ensured by controlling the temperature and time of the oxidation reaction and the fluorination reaction and the proportion of raw materials.

The purification method provided by the invention has the advantages of simple operation, simple raw materials, cheap equipment and lower cost, and the purity of the silicon carbide micro powder can reach the conventional silicon carbide semiconductor production standard.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The purification of the beta-silicon carbide dry powder material produced by the company A comprises the following steps:

(1) adding 45mL of deionized water into 30g of silicon carbide dry powder with the purity of 90% (the impurity content in the silicon carbide dry powder is 10 wt%), mixing, adding 4.5mL of sulfuric acid solution with the mass concentration of 60%, mixing, carrying out oxidation reaction in a constant-temperature water bath kettle, cooling to room temperature after the oxidation reaction is finished, adding tap water into a product obtained by cooling, mixing, sequentially settling and discharging supernatant to obtain silicon carbide suspension with the pH value of 4; wherein the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: 0.15 mL; the volume ratio of the mass of the silicon carbide dry powder to the water is 1 g: 1.5 mL; the temperature of the oxidation reaction is 90 ℃ and the time is 30 min;

(2) adding 3mL of hydrofluoric acid with the mass concentration of 30% into the silicon carbide suspension obtained in the step (1), carrying out fluorination reaction in a constant-temperature water bath, cooling to room temperature after the fluorination reaction is finished, repeatedly cleaning and filtering with tap water until the pH value is 6.6, repeatedly cleaning and filtering with purified water for 3 times, and drying to obtain beta-silicon carbide micropowder; wherein the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is 10 g: 1 mL; the temperature of the fluorination reaction was 90 ℃ for 30 min.

And (3) detecting the purity of the obtained beta-silicon carbide micro powder, wherein the purity is 99.42%, and the chemical reaction time in purification is 1 h.

FIG. 1 is a macroscopic view of a suspension obtained after mixing a dry powder of silicon carbide with water in example 1; FIG. 2 is a macroscopic view of a suspension obtained by completion of the fluorination reaction in example 1; FIG. 3 is a macroscopic view of the fine β -silicon carbide powder purified in example 1. As can be seen from fig. 1 and 2, a chemical reaction occurs during the purification process.

Example 2

The purification of the beta-silicon carbide dry powder material produced by the company A comprises the following steps:

(1) adding 45mL of deionized water into 30g of silicon carbide dry powder with the purity of 90% (the impurity content in the silicon carbide dry powder is 10 wt%), mixing, adding 6mL of sulfuric acid solution with the mass concentration of 60%, mixing, carrying out oxidation reaction in a constant-temperature water bath kettle, cooling to room temperature after the oxidation reaction is finished, adding tap water into a product obtained by cooling, mixing, sequentially settling and discharging supernatant to obtain silicon carbide suspension with the pH value of 4; wherein the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: 0.2 mL; the volume ratio of the mass of the silicon carbide dry powder to the water is 1 g: 1.5 mL; the temperature of the oxidation reaction is 90 ℃ and the time is 30 min;

(2) adding 3mL of hydrofluoric acid with the mass concentration of 30% into the silicon carbide suspension obtained in the step (1), carrying out fluorination reaction in a constant-temperature water bath, cooling to room temperature after the fluorination reaction is finished, repeatedly cleaning and filtering with tap water until the pH value is 6.6, repeatedly cleaning and filtering with purified water for 3 times, and drying to obtain beta-silicon carbide micropowder; wherein the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is 10 g: 1 mL; the temperature of the fluorination reaction was 90 ℃ for 30 min.

And (3) detecting the purity of the obtained beta-silicon carbide micro powder, wherein the purity is 99.50%, and the chemical reaction time in purification is 1 h.

Example 3

The purification of the beta-silicon carbide dry powder material produced by the company A comprises the following steps:

(1) adding 150mL of deionized water into 100g of silicon carbide dry powder with the purity of 90% (the impurity content in the silicon carbide dry powder is 10 wt%), mixing, adding 20mL of sulfuric acid solution with the mass concentration of 60%, mixing, carrying out oxidation reaction in a constant-temperature water bath kettle, cooling to room temperature after the oxidation reaction is finished, adding tap water into a product obtained by cooling, mixing, sequentially settling and discharging supernatant to obtain a silicon carbide suspension with the pH value of 4.2; wherein the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: 0.2 mL; the volume ratio of the mass of the silicon carbide dry powder to the water is 1 g: 1.5 mL; the temperature of the oxidation reaction is 90 ℃ and the time is 30 min;

(2) adding 10mL of hydrofluoric acid with the mass concentration of 30% into the silicon carbide suspension obtained in the step (1), carrying out fluorination reaction in a constant-temperature water bath, cooling to room temperature after the fluorination reaction is finished, repeatedly cleaning and filtering with tap water until the pH value is 6.8, repeatedly cleaning and filtering with purified water for 3 times, and drying to obtain beta-silicon carbide micro powder; wherein the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is 10 g: 1 mL; the temperature of the fluorination reaction was 90 ℃ for 30 min.

And (3) detecting the purity of the obtained beta-silicon carbide micro powder, wherein the purity is 99.80%, and the chemical reaction time in purification is 1 h.

Example 4

The beta-silicon carbide dry powder material produced by the company B is purified by the following steps:

(1) adding 150mL of deionized water into 100g of silicon carbide dry powder with the purity of 90% (the impurity content in the silicon carbide dry powder is 10 wt%), mixing, adding 20mL of sulfuric acid solution with the mass concentration of 60%, mixing, carrying out oxidation reaction in a constant-temperature water bath kettle, cooling to room temperature after the oxidation reaction is finished, adding tap water into a product obtained by cooling, mixing, sequentially settling and discharging supernatant to obtain silicon carbide suspension with the pH value of 4; wherein the volume ratio of the mass of the silicon carbide dry powder to the sulfuric acid solution is 1 g: 0.2 mL; the volume ratio of the mass of the silicon carbide dry powder to the water is 1 g: 1.5 mL; the temperature of the oxidation reaction is 90 ℃ and the time is 30 min;

(2) adding 10mL of hydrofluoric acid with the mass concentration of 30% into the silicon carbide suspension obtained in the step (1), carrying out fluorination reaction in a constant-temperature water bath, cooling to room temperature after the fluorination reaction is finished, repeatedly cleaning and filtering with tap water until the pH value is 6.6, repeatedly cleaning and filtering with purified water for 3 times, and drying to obtain beta-silicon carbide micro powder; wherein the volume ratio of the mass of the silicon carbide dry powder to the hydrofluoric acid is 10 g: 1 mL; the temperature of the fluorination reaction was 90 ℃ for 30 min.

And (3) detecting the purity of the obtained beta-silicon carbide micro powder, wherein the purity is 99.60%, and the chemical reaction time in purification is 1 h.

From the above examples, it can be seen that the purification method provided by the invention can be used for efficiently purifying the silicon carbide micro powder, and the obtained silicon carbide micro powder has high purity.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.